Multiobjective shape optimization of speed humps

This paper presents a new approach to the shape optimization of road speed humps. The proposed approach is based on multiobjective genetic optimization of the hump profile while taking into account the separation phenomenon, which occurs when the front tires of the vehicle momentarily lose contact with the road surface. The optimization is carried out for speeds up to twice the authorized speed (throughout this article, the term authorized speed refers to speed limits enforced in speed reduction [bump] areas of the roads) rather than for illegally high speeds as adopted by many of the previous works. A 6-degree of freedom non-linear dynamic model is used to identify the speeds at which separation occurs, and hump profiles associated with these speeds are discarded as infeasible solutions. Three independent objective functions are selected for optimization. They include the maximum vertical acceleration experienced by the driver when crossing the hump below the authorized speed limit (to be minimized), the same vertical acceleration at speeds above the authorized speed (to be maximized), and the ascending ratio of the “speed—vertical acceleration” curve (to be maximized). These objective functions are evaluated for more than 10,000 humps of two popular profile types (sinusoidal and flat top with straight ramps) and optimum profiles for three speed limits of 20, 25, and 30km/h are determined using the multiobjective nondominated sorting genetic algorithm II. As a result, a Pareto front of at least ten optimal points is achieved for each of the two hump profile types. Furthermore, to incorporate the economical aspects of the real-world problem, Pareto optimal points for the two profile types were compared based on their lateral section areas (an indication of the manufacturing cost). The comparison shows that sinusoidal humps more often than not outdo their flat top rivals economically.     

Frequency- and time-varying scattering parameters of a photo-excited superconducting microbridge

The extended scattering parameters for linear time varying devices are used to model a high-temperature superconducting (HTS) bridge under time-harmonic optical irradiation. It is shown that this structure acts as a time-varying low-pass filter, which its transfer function characteristic changes periodically with time. This behavior makes this configuration ideal for applications where a time-varying filter is on demand.     

A suggested new profile for externally pressurized power screws

In general, the traditional types of power screws may be considered as ordinary screw threads with certain dimensional restrictions recommended to improve their dry working performance. However, when applying the theory of externally pressurized lubrication to such machine elements, it may be inconvenient to confine the study to such constraints. The problem is investigated considering the general form of the screw thread; the optimum combination of the thread parameters for the most suitable externally pressurized power screw are determined.A new profile for externally pressurized power screws is suggested and proved to be more convenient and efficient than the ordinary profiles.     

Engineering behavior of the Lisan Marl as a dyke foundation material: Dead Sea,Jordan

Problems have occurred with dykes constructed on the Lisan Marl to retain brine pumped from the Dead Sea, which is chemically processed to produce potash. In this study the engineering behavior, collapse potential and compressibility of the Lisan Marl were assessed by undertaking laboratory tests with both natural, distilled water and brine as the media. The results showed that the liquid limit and fine particles increased when the soil was mixed with fresh/distilled water compared with brine water. The soil can be classified as highly compressible with a low undrained shear strength. In terms of collapsibility, the soil could be classified as slightly collapsible upon inundation with distilled water and moderately collapsible when soaked in Dead Sea brine. The results are important when determining the height and nature of the dykes.      

Thermoeconomic optimization for a finned‐tube evaporator configuration of a roof‐top bus air‐conditioning system

This paper presents a methodology of a design optimization technique that can be useful in assessing the best configuration of a finned‐tube evaporator, using a thermoeconomic approach. The assessment has been carried out on a direct expansion finned‐tube evaporator of a vapor compression cycle for a roof‐top bus air‐conditioning (AC) system at a specified cooling capacity. The methodology has been conducted by studying the effect of some operational and geometrical design parameters for the evaporator on the entire cycle exergy destruction or irreversibility, AC system coefficient of performance (COP), and total annual cost. The heat exchangers for the bus AC system are featured by a very compact frontal area due to the stringent space limitations and structure standard for the system installation. Therefore, the current study also takes in its account the effect of the variation of the design parameters on the evaporator frontal area. The irreversibility due to heat transfer across the stream‐to‐stream temperature difference and due to frictional pressure drops is calculated as a function of the design parameters. A cost function is introduced, defined as the sum of two contributions, the investment expense of the evaporator material and the system compressor, and the operational expense of AC system that is usually driven by an auxiliary engine or coupled with the main bus engine. The optimal trade‐off between investment and operating cost is, therefore, investigated. A numerical example is discussed, in which a comparison between the commercial evaporator design and optimal design configuration has been presented in terms of the system COP and evaporator material cost. The results show that a significant improvement can be obtained for the optimal evaporator design compared with that of the commercial finned‐tube evaporator that is designed based on the conventional values of the design parameters. Copyright © 2007 John Wiley & Sons, Ltd.     

Efficient Treatment of the Vardy–Brown Unsteady Shear in Pipe Transients

An accurate, simple, and efficient approximation to the Vardy–Brown unsteady friction equation is derived and shown to be easily implemented within a one-dimensional characteristics solution for unsteady pipe flow. For comparison, the exact Vardy–Brown unsteady friction equation is used to model shear stresses in transient turbulent pipe flows and the resulting waterhammer equations are solved by the method of characteristics. The approximate Vardy–Brown model is more computationally efficient (i.e., requires one-sixth the execution time and much less memory storage) than the exact Vardy–Brown model. Both models are compared with measured data from different research groups and with numerical data produced by a two-dimensional turbulence waterhammer model. The results show that the exact Vardy–Brown model and the approximate Vardy–Brown model are in good agreement with both laboratory and numerical experiments over a wide range of Reynolds number and wave frequencies. The proposed approximate model only requires the storage of flow variables from a single time step while the exact Vardy–Brown model requires the storage of flow variables at all previous time steps and the two-dimensional model requires the storage of flow variables at all radial nodes.     

Propoxylated Fatty Thiazole,Pyrazole, Triazole,and Pyrrole Derivatives with Antimicrobial and Surface Activity

Lauric acid and propylene oxide were used to modify four biologically active heterocycles (thiazole, pyrazole, triazole, and pyrrole) to synthesize 17 new surfactants. The chemical structures of these surfactants were confirmed using infrared and ¹H, and ¹³C nuclear magnetic resonance (NMR) spectroscopy. The surfactants all show good surface activity, low critical micelle concentration (CMC) values, high cloud points, and tight interfacial packing. All showed antimicrobial activity on both bacteria and fungi. In addition, biodegradation testing demonstrated significant breakdown within seven days.     

Synthesis of novel poly 2‐vinylpyridine‐mixed metal complexes and studying their effect as antitumor chemotherapeutic agents,part 2

The poly2‐vinylpyridine and cationic polymer‐mixed metal complexes (P2VPMC) have been prepared and characterized by analytical measurement such as: molecular weight, elemental analysis, IR‐spectroscopy, NMR‐spectroscopy, XRD, and UV. The degree of N‐alkylation of poly vinyl pyridine (P‐2VP) was 10% determined by chlorine content according to elemental microanalysis. Through ICP instrument the complexation between P‐2VPC and the mixed metal chlorides was proven. The structure of the samples was characterized using X‐ray diffraction. It was found that the complexes have amorphous properties. The antitumor activity of this compound was examined in vitro on cell lines. The results reflect pronounced cytotoxicity of P‐2VPMC against animal experimental EAC cells line, and human, HeLa, HCT116 and Hep‐G2, cell lines. Antitumor activity of the novel compound as applied on mice bearing Ehrlich solid carcinoma, revealed delays tumor growth compared with untreated animals and decreases tumor volume. The antitumor activity of the P2VPMC might be due to its ability to pass through the membrane and interact with, DNA causing cross‐linking action which might be the key factor for great antitumor activity of the P2VPMC compound. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Kinetic study of crude oil-to-chemicals via steam-enhanced catalytic cracking in a fixed-bed reactor

This study presents new experimental results on the direct conversion of crude oil to chemicals via steam-enhanced catalytic cracking. We have organized the experimental results with a kinetics model using crude oil and steam co-feed in a fixed-bed flow reactor at reaction temperatures of 625, 650, and 675°C over the Ce-Fe/ZSM-5 catalyst. The model let us find optimum conditions for crude oil conversion, and the order of the steam cracking reaction was 2.0 for heavy oil fractions and 1.0 for light oil fractions. The estimated activation energies for the steam cracking reactions ranged between 20 and 200 kJ/mol. Interestingly, the results from kinetic modelling helped in identifying a maximum yield of light olefins at an optimized residence time in the reactor at each temperature level. An equal propylene and ethylene yield was observed between 650 and 670°C, indicating a transition from dominating catalytic cracking at a lower temperature to a dominating thermal cracking at a higher temperature. The results illustrate that steam-enhanced catalytic cracking can be utilized to effectively convert crude oil into basic chemicals (52.1% C2-C4 light olefins and naphtha) at a moderate severity (650°C) as compared to the conventional high-temperature steam cracking process.